It is known to package a noncarbonated liquid or a fluent granular foodstuff or the like in a package comprised of a cup- or vessel-like bottom part having a rim to which is sealed a flexible foil. Typically the vessel is made of a rigid synthetic-resin and the foil is made as a metal/plastic laminate that is heat sealed or otherwise attached to the rim of the vessel.
The foil is usually formed with a tab that projects past the rim of the cup. This tab is pulled up away from the cup to strip the foil from the rim by separating the foil and the cup at the rim seal.
It is therefore necessary for the manufacturer to make the seal strong enough to safely contain the contents prior to use, yet weak enough that it can be pulled open without tearing the foil. When the error is in the direction of making the bond too strong, the user frequently tears off the tab or cannot open the package without using a tool, or at the very least some of the contents is spilled from the violence of the opening operation. When the seal is too weak it is opened inadvertently during normal handling and the contents are lost or spoiled.